the root cause of flip-flop charging logic if you insert wall charger

[Andy Green]

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Somebody in the thread at some point said:
| Hi all,
|
| If you insert wall charger to charge Neo, you will find the charging
| indication will be successful and failed one after another.

I saw this when I did the overshoot analysis recently.  I was powering
the device only from USB and not battery --  so I assumed the pcf50633
was pushing the adapter into overcurrent briefly during power-on.  But -->

| The root cause is the signal from VBUS rasies and drops rapidly when
| inserting a wall charger.
| You can see attached picture named defect_usbx_signal.jpg(The other
| picture is a correct VBUS signal which makes correct charging indication).
| In consequence, pcf50633 driver detects a USBINS and USBREM interrupts
| in a schedule work.

It sounds like you were already in Linux doing this, so I wonder what is
the excuse of the adapter now to drop dead briefly on insertion?

| Before this, I could apply this patch to provide correct charging logic.
| Any thoughts?

The effect of your patch is to ignore the case where we find insertion
and removal flags both set, but actually, it's a sign that we have no
idea what our USB insertion status is, it's literally "undefined".

I applied it on to stable, but really we need to do something a bit more
complicated here and react to the sign that we have no certainty by
going and looking at MBCS1.usbpres after some settling period.

- -Andy
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